add slightly custom mixture example

examples/more/15_time_to_botec_custom_mixture/example.c

@@ -0,0 +1,34 @@
+#include "../../../squiggle.h"
+#include "../../../squiggle_more.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+double cumsum_p0 = 0.6;
+double cumsum_p1 = 0.8;
+double cumsum_p2 = 0.9;
+double cumsum_p3 = 1.0;
+
+double sampler_result(uint64_t * seed)
+{
+
+    double p = sample_uniform(0, 1, seed);
+    if(p< cumsum_p0){
+        return 0;
+    } else if (p < cumsum_p1){
+        return 1;
+    } else if (p < cumsum_p2){
+        return sample_to(1,3, seed);
+    } else {
+        return sample_to(2, 10, seed);
+    } 
+}
+
+int main()
+{
+
+    int n_samples = 1000 * 1000, n_threads = 16;
+    double* results = malloc((size_t)n_samples * sizeof(double));
+    sampler_parallel(sampler_result, results, n_threads, n_samples);
+    printf("Avg: %f\n", array_sum(results, n_samples) / n_samples);
+    free(results);
+}